Study On Acid-metal Synergistic Catalytic Preparation Of Chemicals From Xylose And Furfural

Lignocellulosic biomass has the advantages of carbon neutrality,large reserves and renewable,which has attracted extensive attention from researchers.As the basic building block of hemicellulose,xylose has become a research hotspot in the field of biomass to catalyze the conversion of xylose into high-value chemicals.This paper focuses on the catalytic conversion of xylose and furfural(xylose dehydrated derivatives).The specific research content includes the following two aspects:1.The conversion process of xylose to diol(ethylene glycol,1,2-propanediol)was studied.The reaction characteristics of bicenter tandem conversion xylose were studied from the aspects of acidhydrogenation active site combination,catalyst preparation method,and acid-hydrogenation active site ratio.Firstly,the effects of hydrogenated metals(Ru,Pt,Pd,Ni)and acids(ZrO2,SnO2,Ga2O3,MnO2,WO3,H-Beta)on the catalytic conversion of xylose were investigated.With Lewis acid as the acid center,the product distribution was ethylene glycol,1,2-propanediol,and acetone alcohol.With Bronsted acid as the acid center,the total yield of the product is low.When WO3 is the acid center,the C2 diol yield is higher than that of C3 diol,which may be different from the mechanism of WO3 and other oxides to catalyze the condensation reaction of xylose anti-hydroxylal.In the M/MOx system,when the proportion of control metal/acid is low,the yield of C3 diol in the system is much higher than that of C2 diol,when the ratio of the two is increased,the yield of C2 diol increases significantly,and the ratio of C3 diol to C2 diol is close to the theoretical value of 1:1,of which the combination of Ni and MnOx is the best.Acid-metal dual-active position catalysts(Ni/C+MnOx,Ni/MnOx,Ni-MnOx/AC)with different structures were prepared by controlling the same Ni:MnOx molar ratio,and the results showed that the Ni-MnOx/AC catalyst prepared by co-impregnation method catalyzed xylose conversion to prepare diols with the best effect.Furthermore,by optimizing the process conditions,91.28%diol yield was obtained,including 45.06%ethylene glycol yield and 46.22%1,2-propanediol yield.2.The reaction process of furfural to cyclopentanone was studied.Based on the reaction mechanism of acid-hydrogenation bicenter catalytic furfural first hydrogenation to furfuryl alcohol,then acid hydrolysis ring rearrangement to cyclopentanone.The activation energy of Ru,Pt,Pd,Ni and other active centers catalyzed the hydrogenation of furfural to furfuyl alcohol was investigated,and the results showed that the activation energy increased in the order of Pt<Pd<Ru<Ni,and Pt was preferred as the hydrogenation center for the preparation of cyclopentanone from furfural.The Pt@S-1 catalyst was prepared by confined zeolite encapsulation,and compared with Pt/S-1,it maintained the high selectivity of furfuryl alcohol of 91.81%and had excellent recycling performance.On this basis,Zr with excellent performance reported in the literature was used as the acid center,and the(Pt+Zr)@S-1 catalyst was synthesized to obtain a carbon yield of 57.30%and a selectivity of 55%for cyclopentanone.Taking Cu with high furfuryl alcohol selectivity but lower price as the hydrogenation center,(Cu+Zr)@S-1 catalyst was prepared,and under the optimal reaction conditions,the selectivity of cyclopentanone in the product was 93.72%,but due to the influence of molecular sieve micropores,there were significant hydrogen mass transfer limitations,and only 56%carbon yield was obtained.The catalyst preparation method was changed,Cu/ZrO2 catalyst was prepared by ball milling,the calcination temperature,molar ratio of acid and hydrogenated metal,acid active site and other factors were investigated,and the carbon yield of 76.97%was obtained by optimizing the reaction conditions,and only cyclopentanone alcohol was included in the product,while the selectivity of Cu/ZrO2 catalyst prepared by precipitation method was significantly reduced.The characterization results show that the Cu/ZrO2 catalyst prepared by ball milling has more Cu and ZrO2 interfaces,which is conducive to the preparation of cyclopentanone by acid-hydrogenation bicenter catalyzed furfural.Compared with the precipitation method,the ball milling method presents significant advantages in the control of the drop point of multiple components.